This section provides background information related to the present disclosure which is not necessarily prior art.
The integration degree of semiconductor devices are increasing as the integration process thereof is rapidly developing. Designers have put effort into assembling more semiconductor devices in a smaller area, so that miniaturization of the apparatus is realized. To ensure a stable operation of these highly integrated semiconductor devices, the heat produced by each of the devices must be transferred to the ambient environment effectively and promptly.
A common process is installing a heat sink made from metals with high thermal conductivity, such as copper or aluminum, on the surface of the electronic components integrated with the semiconductor devices to increase the cooling area. But the surfaces of the electronic components and the heat sinks are not absolutely even. Thus, air gaps inevitably emerge when the uneven surfaces come into contact, which air gaps may result in a significant decrease in cooling effectiveness. Therefore, thermally conductive materials are used to fill the air gaps between the heat sink and the electronic components in order to allow a better thermally conductive pathway between the surfaces as well as a better cooling effect.
Thermally conductive silicone greases and phase change or transition materials have good thermal conductivity but poor electrically insulating properties, and thus are not suitable in those situations where high electrical insulation is needed. A flexible gap filling material with thermal conductivity exhibits certain electrical insulation, but cannot be used in those situations where high electrical insulation is needed. Such a material is only suitable for applications with low pressure, whereas it is not qualified in the fields like high power supplies and automobiles.
A thermally conductive, electrically insulating material having both good thermal conductivity and electrical insulating properties would be capable of solving the problem of achieving good thermal conductivity with high electrical insulating properties. A thermally conductive, electrically insulating material can effectively link a device with a heat sink and provide a thermally conductive channel to reduce thermal resistance and provide good electrically insulating properties to ensure normal operation of the device.
One traditional thermally conductive electrically insulating material is a fully-cured silicon resin composite. This example generally uses a silicon resin as the matrix, and ceramic materials (e.g., aluminum oxide, aluminum nitride or zinc oxide, etc.) as fillers. Because the fully-cured silicon resin lacks adhesion on its surfaces when applied, it may easily slip or shift during the process when the electrically insulating material is mounted onto a heat sink or device in particular during operation on a vertical plane.
To impart adhesion to the material surface, one common method that is frequently employed is to attach a double-sided adhesive tape onto the surface of the thermally conductive electrically insulating material. The tape provides the thermally conductive electrically insulating material with certain adhesion on its surfaces. But this method has a number of disadvantages. For example, the thermally conductive electrically insulating material has such a low surface energy such that the tape cannot adhere directly on the surface. Thus, it is necessary to use expensive silica gel tapes or additionally treat the thermally conductive electrically insulating material by corona and the like to increase the surface energy of the material so that an adhesive tape may be applied subsequently on the surface. The use of silica gel tape will undoubtedly increase the cost, while the corona process tends to deteriorate properties of the material, particularly insulation. The double-sided adhesive tape has a low thermal conductivity, such that the tape decreases the overall thermally conductive effect of the thermally conductive electrically insulating material. Also, it is difficult to use or laminate adhesive tape on both sides of the thermally conductive electrically insulating material. Therefore, the range of use is limited for such a thermally conductive electrically insulating material with double-sided adhesive tape.